SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.short_description, 
  IF(
    cscart_product_descriptions.short_description = '' 
    OR cscart_product_descriptions.short_description IS NULL, 
    cscart_product_descriptions.full_description, 
    ''
  ) AS full_description 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    87185, 87202, 87219, 90802, 87186, 87203, 
    87220, 90803, 87183, 87200, 87217, 
    90800, 87181, 87198, 87215, 90798, 
    87184, 87201, 87218, 90801, 85014, 
    85020, 85026, 85032, 87182, 87199, 
    87216, 90799, 87180, 87197
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00080

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "13.52"
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 30,
      "rows_produced_per_join": 30,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "10.52",
        "eval_cost": "3.00",
        "prefix_cost": "13.52",
        "data_read_per_join": "114K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (87185,87202,87219,90802,87186,87203,87220,90803,87183,87200,87217,90800,87181,87198,87215,90798,87184,87201,87218,90801,85014,85020,85026,85032,87182,87199,87216,90799,87180,87197)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
85014 Hudson Reed Solar Floor Standing 2 Drawer Vanity Cabinet 800mm - Pure White
85020 Hudson Reed Solar Floor Standing 2 Drawer Vanity Cabinet 800mm - Cool Grey
85026 Hudson Reed Solar Floor Standing 2 Drawer Vanity Cabinet 800mm - Indigo Blue
85032 Hudson Reed Solar 800mm Floor Standing 2-Drawer Unit - Fern Green
87180 Old London Floor Standing 2 Door Basin Unit 600mm - Storm Grey
87181 Old London Floor Standing Angled 2 Door Basin Unit 600mm - Storm Grey
87182 Old London Floor Standing 2 Door Basin Unit 800mm - Storm Grey
87183 Old London Floor Standing Angled 4 Door Basin Unit 1000mm - Storm Grey
87184 Old London Floor Standing 2 Door Basin Unit 1000mm - Storm Grey
87185 Old London Floor Standing Angled 4 Door Basin Unit 1200mm - Storm Grey
87186 Old London Floor Standing 4 Door Basin Unit 1200mm - Storm Grey
87197 Old London Floor Standing 2 Door Basin Unit 600mm - Twilight Blue
87198 Old London Floor Standing Angled 2 Door Basin Unit 600mm - Twilight Blue
87199 Old London Floor Standing 2 Door Basin Unit 800mm - Twilight Blue
87200 Old London Floor Standing Angled 4 Door Basin Unit 1000mm - Twilight Blue
87201 Old London Floor Standing 2 Door Basin Unit 1000mm - Twilight Blue
87202 Old London Floor Standing Angled 4 Door Basin Unit 1200mm - Twilight Blue
87203 Old London Floor Standing 4 Door Basin Unit 1200mm - Twilight Blue
87215 Old London Floor Standing Angled 2 Door Basin Unit 600mm - Timeless Sand
87216 Old London Floor Standing 2 Door Basin Unit 800mm - Timeless Sand
87217 Old London Floor Standing Angled 4 Door Basin Unit 1000mm - Timeless Sand
87218 Old London Floor Standing 2 Door Basin Unit 1000mm - Timeless Sand
87219 Old London Floor Standing Angled 4 Door Basin Unit 1200mm - Timeless Sand
87220 Old London Floor Standing 4 Door Basin Unit 1200mm - Timeless Sand
90798 Old London 750mm 3-Door Basin Unit - Hunter Green
90799 Old London 800mm 2-DOOR BASIN UNIT - Hunter Green
90800 Old London 1000mm 4-Door Basin Unit - Hunter Green
90801 Old London 1000mm 2-DOOR BASIN UNIT - Hunter Green
90802 Old London 1200mm 4-Door Basin Unit - Hunter Green
90803 Old London 1200mm 4-Door Basin Unit - Hunter Green